Traveling diet body scales
A digital body weight scale that is no bigger than 20cm x 10cm x 3cm. It could have a ruggedized LCD for readouts, or simply incorporate a bluetooth chip and send the results to your cellphone or laptop.
The way I envision it working, is that you put it on the floor and balance on top of the device on one foot. When the scale has gotten a constant and steady strain for over 1 second it gives a beep, at which point you can pick it up and read the results, or as I said, they could be bluetoothed to another device.
For people who weigh themselves daily, yet need to travel, this would be great: digital body scales are pretty inexpensive, but currently they are all big and bulky. I don't see why the strain gauge technology used in them couldn't be packaged in a travel package.
Reward: At least one device for free.